The Burden of Influenza in Young Children, 2004–2009

Abstract

OBJECTIVE: To characterize the health care burden of influenza from 2004 through 2009, years when influenza vaccine recommendations were expanded to all children aged ≥6 months. METHODS: Population-based surveillance for laboratory-confirmed influenza was performed among children aged <5 years presenting with fever and/or acute respiratory illness to inpatient and outpatient settings during 5 influenza seasons in 3 US counties. Enrolled children had nasal/throat swabs tested for influenza by reverse transcriptase-polymerase chain reaction and their medical records reviewed. Rates of influenza hospitalizations per 1000 population and proportions of outpatients (emergency department and clinic) with influenza were computed. RESULTS: The study population comprised 2970, 2698, and 2920 children from inpatient, emergency department, and clinic settings, respectively. The single-season influenza hospitalization rates were 0.4 to 1.0 per 1000 children aged <5 years and highest for infants <6 months. The proportion of outpatient children with influenza ranged from 10% to 25% annually. Among children hospitalized with influenza, 58% had physician-ordered influenza testing, 35% had discharge diagnoses of influenza, and 2% received antiviral medication. Among outpatients with influenza, 7% were tested for influenza, 7% were diagnosed with influenza, and <1% had antiviral treatment. Throughout the 5 study seasons, <45% of influenza-negative children ≥6 months were fully vaccinated against influenza. CONCLUSIONS: Despite expanded vaccination recommendations, many children are insufficiently vaccinated, and substantial influenza burden remains. Antiviral use was low. Future studies need to evaluate trends in use of vaccine and antiviral agents and their impact on disease burden and identify strategies to prevent influenza in young infants.

Estimating the burden of seasonal influenza in Spain from surveillance of mild and severe influenza disease, 2010‐2016

“…During the 6 studied influenza seasons, we found that, while children under the age of 15 years have the highest ILI and MCIC rates, the very young (0‐4 years) and the elderly exhibit the highest rates of severe influenza‐associated hospitalizations. This is consistent with previous studies showing that young children and adolescents have the highest rates of medically attended influenza,7, 12, 13, 14 while the highest hospitalization rates for influenza are observed among very young15 and persons aged ≥65 years 16. Previous exposure to influenza viruses, providing a partial immunity to the circulating viruses, and higher vaccine coverage than in other age‐groups,17, 18 could account for the lower ILI rates at the primary care level in the elderly population.…”

Estimation of influenza‐attributable medically attended acute respiratory illness by influenza type/subtype and age, Germany, 2001/02–2014/15

“…Population‐based studies have shown that the actual burden of influenza in children is under‐recognized with common (ILI) surveillance methods. For example, between 2004/05 and 2008/09 Poehling conducted a population‐based study in three US counties and found that per season, between 10% and 25% of children aged 0‐4 years sought outpatient medical care because of influenza 15. Our estimates in these two age groups between the seasons 2002/03 and 2008/09 ranged from 2% to 17% (age group 0‐4; median 11%) and from 3% to 13% (age group 5‐14; median 8%), respectively, and are therefore comparable with the thoroughly conducted population‐based research study.…”

The impact of respiratory viruses on lung health after preterm birth

“…The burden of influenza is inversely related to age, with 50% of influenza-related hospitalisations occurring in infants younger than 6 months of age [120,122]. Data from a wide population-based study of children under 5 years who were admitted to hospital or presented to outpatient clinic with an acute respiratory illness, over five influenza seasons, showed that 35% of hospitalised children and 7% of outpatient children had laboratory-confirmed influenza, despite the extended vaccination recommendations in the population studied [123]. The long-term impact of influenza-related respiratory illnesses during early life is largely unknown, particularly among preterm infants.…”